All-wave antenna system



Feb. 6, 1940. w.'1 CARLSON ET AL ALL-WAVE ANTENNA SYS TEM Filed April50, 1937 2 Sheets-Sheet 1 Ill Mil i FWD/0 Wf/VOEA L L I, r I/ (I ttornegFeb. 6, 1940. w. L. CARLSON ET AL ALL-WAVE. ANTENNA SYSTEM Filed April30, 1937 2 Sheets-Sheet 2 Wmtomeg I Patented Feb. 6, 1940 UNlTED STATESPATENT orrics ALL-WAVE ANTENNA SYSTEM Application April 30,

6 Claims.

Our invention relates to antenna systems. Specifically, our inventionrelates to an all-wave antenna system and the means for coupling saidsystem to a radio receiver.

In all-wave receiving systems, it has been considered desirable to useoneor more dipole antennas, which are coupled through suitabletransformers and a transmission line to the radio receiver. The dipoleantenna or antennas, as often more than one are required, are responsiveto the waves of a few meters length. The dipoles act as an ordinarycapacity antenna for waves of the present broadcasting band. Suchsystems generally require considerable space and two or more supports,which are often not available in the urban areas where the foregoingsystems are most useful in the reduction of man-made interference.

Our present antenna system may be used in connection with almost anytype of antenna conductor. For example, a vertical wire, such as a metalfishing rod or Water pipe, a vertically arranged wire, an L antenna, a Tantenna, a V antenna or an umbrella antenna may be used. Not only is ourpresent system especially adapted to existing forms of antennaconductors, but we have found that the signal to noise ratio shows animprovement over many dipole installations. Our invention may beinstalled in a space which is smaller than for all-wave dipoleinstallations.

We have been able to balance out a large amount of interferingelectrical impulses by carefully arranging a symmetrical or balancedcircuit. While some of the symmetry is obtained by a conventionaltransmissionline, the larger portion is effected by a novel constructionof the coupling means which connect the antenna to the line and the lineto the receiver. We have found that capacity coupling between theprimary and secondary circuits of the coupling means and between thesecircuits and ground should be minimized and the mutual inductivecoupling made as large as possible. These two requirements lead inopposite directions: if the capacity is minimized, the inductivecoupling is reduced; while an increase in inductive coupling ordinarilytends to increase the capacity effects. The capacity coupling issubstantially eliminated by an electrostatic shield. The capacity toground is reduced by suitable spacing and arrangement of the windings ofthe coupling transformers. This in turn reduces the mutual inductivecoupling which is restored to the required value .by a magnetite core.Other means for 1937, Serial No. 140,037

balancing and the like are provided which will be hereinafter described.

One of the objects of our invention is to provide means for coupling anall-wave antenna to an all-wave receiver.

Another object is to provide means for coupling an all-wave antenna to atransmission line.

Another object is to provide means for coupling an all-wave receiver toa transmission line.

A further object is to provide a coupling means which is characterizedby low capacity couplings, tight magnetic couplings, and balancedcircuits.

A still further object is to provide means for improving the signal tonoise ratio in a receiver by balancing out undesired electricalimpulses.

Other objects will appear in the following specification, which may bebest understood by referring to the accompanying drawings in which:

Figure l is a schematic circuit diagram of one. 20 embodiment of ourinvention,

Figures 2, 3 and 4 are illustrations of our invention applied to severaldifferent forms of antenna conductors,

Figure 5 is an elevational view of the balanced coupling means,

Figure 6 is a sectional view of the windings of the couplingtransformer,

Figure 7 is an elevational view of a suitable electrostatic screen, and

figure 8 illustrates a modification of our invention. i

In Fig. 1, an antenna l is coupled through a capacitor 3 to a primarywinding 5, which is suitably grounded as indicated by reference numerall. The primary 5 is symmetricallyv coupled to a balanced secondary,which is composed of bifilar windings 9 and El, which are coupledtogether by a capacitor 3. The antenna l is also connected to a secondtransformer l5, which consists of a primary winding ll and a secondarywinding IS. The terminals of. the secondary winding are connected to thecapacitor la. The transformers preferably include a magnetite core 2|.The transformer is housed in a container of any suitable mate rial, suchas aluminum, copper, or the like, 23. The container may be filled with aweatherproofing material, such as wax, etc.

The terminals of the windings ll and H, which are not connected to thecapacitor 13, are joined to one pair of terminals of a transmission line25. This line may be a twisted pair of conductors, which are suitablyinsulated from each other and from ground. The other or remote pair ofterminals of the transmission line 2'5 are connected 55 to a secondcoupling means 21, which couples the transmission line to a radioreceiver 28 of the allwave type. The input terminals of the radioreceiver 28 are represented by the binding posts 25, 1

3!. The coupling means 2'! is similar to the antenna coupling meanspreviously described. An exception is that an electrostatic shield 33 ispositioned between the primary windings 35, 31, and secondary windings4|, 47 of'the transformers.

The present coupling means 21 includes bifilar primary windings 3?,which are joined by a capacitor 39. A secondary winding 4| issymmetrically coupled to the bifilar windings. One terminal of thesecondary winding 4! is grounded. The other terminal is connectedthrough a 'capacitor 43 to the antenna binding post 29. A secondtransformer consists of a primary; 45, which is connected across thecapacitor .39, and a secondary 4'1. One of the terminals of thesecondary 57 is connected to ground and to the binding post 3!. Theother terminal of the secondary is connected to the antenna binding post29. Thetransformers include amagnetite core 43. A metal containerisprovided around the transformers and is grounded to the receiverchassis.

The operation of the circuits thus describedis briefly as follows: I

High frequency signaling currents pass from the antenna through thecapacitor 3 and the transformer primary 5 to ground. These currentsinduce circulating currents in the secondary windings '9, H andtransmission line 25. These circulating currents flowing through theprimary windimgsv 35, 37 induce currents in. the secondary winding M,which flow through the coupling capacitor 43 to the antenna binding post2?] and to I the grounded binding post ill. When signaling currents ofthe broadcast frequency range are impressed upon the antenna I, thesecurrents flow through the primary winding I! to ground and inducecurrents in the secondary winding iii. The induced currents arecirculated through the transmission line 25 and the primary 15. The

currents flowing through theprimary 15 induce currents which flowthrough the secondary il to ground and to the antenna binding post 29.

The reactances of the capacitors 3, i3, 39 and 43 are low for highfrequency currents, as compared with their reactance for currents of thebroadcast frequency range. It will be seen from inspection that thecircuits are symmetrically arranged and, therefore, balanced.

It will also be observed that the antenna l is preferably of a typewhich may be insulated from ground. The ground connection I should bemade close to the antenna termination and may consist of a suitableconductor imbedded in the earth near the antenna or a counterpoise. Ineither event, we have found that a good ground adjacent to the antennais highly desirable in the reduction of the effect of disturbingelectrical impulses.

We have also found it desirable to arrange the coupling means adjacentthe base of the antenna so that the leads to the transformer and toground are made as short as possible. The second coupling means 2? ispreferably arranged as near the receiver as possible to thereby shortenthe lengths of the connecting leads. The receiver and the coupling means23 are preferably connected to a ground which is independent of theground I at the antenna.

As previously pointed out, one of the advantages of the antenna systemof our invention is its adaptability to numerous types of antennas. InFig.- 2, an L antenna 49 is supported by an insulator 5!, which isfastened to a mast 53. The antenna coupling means is housed in awaterproof container 55. The ground is represented by a counterpoise5'1, which may be a conductive screen, a metal roof, or a metal flashingon the roof. If. the mast is supported on the earth, the ground may be aburied screen, counte-rpoise or the like. The transmission line isrepresented as a twisted pair of conductors 59, which are suitablyinsulated from each other and from ground.

In Fig. 3, the antenna conductor is represented as a metal rod 6!, whichis suitably insulated from ground by a base insulator 63. We have foundthat the antenna conductor may be made from six feet high to thirty ormore feet depending upon location and freedom from shielding objects.The antenna lead 65 is connected from the base or. the conductor (ii tothe antenna coupling means'fil. The ground connection is represented asa. metal roof or metal flashing 69.

In Fig. 4, an umbrella type antenna is represented by conductors H,which are insulated at the top of the mast 13 by an insulating support75. The wires II are insulated from. earth by insulators 77. Severalwires of the antenna are connected by lead-ins 79 to the coupling meansill, which is grounded by a ground pipe 83. The coupling between theantenna and the receiving transformer, which is not shown, isrepresented by a transmission line 85.

By Way of example, the antenna may be from 20 to 40 feet high and, if anL antenna is used, from 30 to 60 feet long. Antennas of the foregoingdimensions have shown efficient response over the present standardbroadcast band of 550 to 1600 kilocycles, with a correspondingeiiiciency in the short-wave broadcast band covering from approximately5. megacycles to 20 megacycles. The ground, system. adjacent the antennamay be a few square feet of screening buried six inches under thesurface of the earth, or a ground pipe of the order of one inchdiameter, which is driven into the earth about four feet.

The transmission line to set coupling means is represented in Figs. 5and 6. A metal shield 81 is arranged with insulating supports 89, 9! atits ends. These supports engage the ends of a winding form 93. Thewinding form will be more fully illustrated by Fig. 6, which ishereinafter described. The coupling capacitors 95, 91 are supported onthe insulators 89 and 9! respectively. This minimizes the couplingeffect between the capacitors. The capacitors are preferably of smallphysical dimensions. The capacitors are symmetrically positioned withrespect to the shield 8! and spaced therefrom. It will be observed thatthe input terminals 89 are arranged at one end of the transformer, whilethe output leads it)! are arranged at the opposite end to minimize overall capacity coupling.

The transformer windings are shown in Fig. 6. In this figure aninsulated tube H33 supports the primary windings Hi5. These windings arepreferably of the bifilar type to insure a symmetrical arrangement ofthe windings with respect to their secondary. The primary winding ml forthe broadcast frequency range is also I supported on the tube 33. Amagnetite core I08 sulating .tube H9 is positioned on the outside of theshield Ill. The secondary windings IZI and I23 are supported by thelast-mentioned tube II9. These windings are arranged in juxtapositionwith respect to the primary windings I05 and II", respectively. Thewinding I23 is preferably of the multi-layer type.

Figure 7 represents a suitable embodiment of an. electrostatic shield.This shield is composed of a series of parallel conductors I25, whichare insulated from one another and supported by cotton threads I27,which are woven through the conductors I25. This construction forms acloth which includes a plurality of parallel conductors. Theseconductors I 25 are connected together at one end by a conductor I29,which is grounded. This electrostatic shield, as is well known,eliminates or minimizes capacity coupling without preventing mutualmagnetic coupling. The primary windings I05, ID! are spaced from theshield III to thereby minimize the capacity from these windings to theshield and to ground.

In Fig. 8 the ground rod [FM is also used as a support for an antennaconductor I53. The antenna conductor may be metal pipe, seamless metaltubing, a metal rod or the like. The ground rod is threaded or suitablyflanged to receive an insulator I55. The antenna conductor is mounted onthis insulator by a threaded portion, bayonet fitting or any socketconnection. The transformer input leads I5'I, I59 are connected to theantenna condctor I53 and ground rod I5I as shown.

In the design of the broadcast portions of the coupling transformers weprefer not to match the surge impedance of the transmission line. Theline is preferably treated as a capacity. This capacity is used toresonate the windings to which it is connected. The several windings andcapacities are so arranged that the antenna circuit, the line circuitand the receiving set input circuit are each resonant to substantiallythe middle frequency of the broadcast frequency range. The tightcoupling between the circuits broadens the response of the network. There-.

sulting characteristic is a three-peak response curve whichsubstantially covers the broadcastfrequency range. We have found thatthe resonant conditions of the line varies with changes in line length.The effects of changes in line length are relatively small and maybeneglected within the ordinary limits of ahome antenna installation.

We have found that the selectivity characteristics of the receiver areapparently varied for frequencies removed from the resonant frequency ofthe receiver. For example, the antenna system may resonate atfrequencies differing from the frequency of reception and thus reducethe apparent selectivity of the receiver. These effects aresubstantially reduced by including a small amount of resistance in theantenna, transmission line, or receiver input circuit. One convenientarrangement for including this resistance is to wind the primary orsecondary of the broadcast section of one or both of the transformerswith resistance wire.

We have found that many disturbing noises are transferred to thereceiver through the associated lighting lines to which the receiver isconnected. The disturbing noises, coming in on the power supply, put aradio frequency noise voltage on the chassis of the receiver. It isgenerally difiicult to reduce this voltage by grounding the chassisbecause the ground lead cannot be made short enough to have a lowimpedance. We prefer to reduce these disturbing noises by carefullybalancing the transmission line, and the transformer windings and bysubstantially reducing the capacity coupling between the windings. Inaddition to these precautions, we have found it desirable to ground thesecondary transformer windings tothe radio receiver chassis by shortleads. When thusarranged, the disturbing noises are substantiallyreduced from the secondary circuits of the coupling means connecting thetransmission line to the radio receiver. We prefer to ground theelectrotatic shield to a short lead connected to the radio receiverchassis, as shown in the drawings.

' spect to ground.

We claim as our invention:

1. An antenna system comprising a single antenna conductor; meansinsulating said conductor from ground; a transmission line; meanslocated adjacent said antenna and ground for coupling said antenna to atransmission line,;...

said last mentioned means including a transformer primary winding, aseries capacitor and second transformer primary winding, a low impedanceground connection for said primary windings, connections from said firstnamed primary and said capacitor to said antenna conductor, a core ofmagnetic material within and coaxial to said primary windings, secondarywindings respectively mutually coupled to and substantially spaced formsaid primary windings, and. connections from said secondary windings tosaid transmission .line, and means for coupling the remote terminals ofsaid transmission line to a radio receiver, said coupling meansincluding a transformer primary winding, a second transformer primarywinding, a core of magnetic material within and coaxial to said primarywindings, secondary windings respectively coupled to and substantiallyspaced from said primary windings, an electrostatic shield between saidprimary and secondary windings and closely associated with saidsecondary windings, a capacitor connected to one of said secondarywindings and to the input terminals of said radio receiver, connectionsfrom the other of said secondary windings to said input terminals andmeans for grounding said radio receiver, said electrostatic shield, andsaid secondary windings.

2. A coupling device including a pair of secondary windings, lowimpedance means for grounding said windings, a capacitor seriallyconnected to one of said windings, a coaxial primary winding within andsymmetrically coupled to one of said secondary windings, butsubstantially spaced therefrom, a pair of balanced coaxial primarywindings serially connected by a capacitor within and mutually coupledto said secondary winding including the first named capacitor,connections from said first named primary winding to said second namedcapacitor,

The coupling means at connections from said balanced primary windings toinput terminals, means for increasing the mutualmagneticcoupling'between said primary and secondary windings, said meanscomprising a magnetic core Within and closely coupled to said primarywinding and means for reducing the capacity coupling between saidprimary and secondary windings, said means comprising a cylindricalelectrostatic shield between said primary and secondary windings,substantially spaced from said primary windings.

3. A coupling device including an outer insulating tube supporting apair of coaxial secondary windings, a capacitor serially connectedbetween one of said windings and an output ter minal, an innerinsulating tube, a pair of annu lar spacers supporting said inner tubewithin and substantially spaced from said outer tube, a primary windingsupported by said inner tube symmetrically coupled to one of saidsecondary windings, a pair of balanced primary windings supported bysaidinner tube, serially connected by a capacitor, and mutually coupledto said secondary Winding including the first named capacitor, a core ofmagnetic material within said inner tube, connections from said firstnamed primary winding to said second named capacitor, and connectionsfrom said balanced 5. A noise reducing antenna system which inv cludesan antenna for receiving radio frequency signals, said antenna beingcharacterized by a common signal path at all frequencies, an antennacoupling transformer located near and connected to an effective groundpotential, an output transformer, a transmission line connecting saidoutput transformer and said antenna transformer, said output transformercomprising a plurality of primary windings closely associated with acore of magnetic material, a plurality of secondary windings, a groundedelectrostatic shield substantially spaced from said priinarywindingsplaced between said primary and secondary windings whereby the capacityfrom said primary windings to said shield is minimized, said secondarywindings being closely associated with said electrostatic shield, and

grounded.

6. A coupling transformer including an outer insulating tube supportinga pair of coaxial secondary windingsadapted to resonate at differentfrequencies, a pair of output terminals, connections from one end ofsaid secondary windings to one of said terminals, connections from theother end of said secondary windings to said other output terminal, aninner insulating tube, a pair of annular spacers supporting said innertube within and substantially spaced from said outer tube, a primarywinding supported by said inner tube, symmetrically coupied to one ofsaid secondary windings but substantially spaced therefrom, a pair ofbalanced primary windings supported by said inner tube, seriallyconnected by a capacitor, and mutually coupled to the other of saidsecondary windings, connections from said first named primary winding tosaid capacitor, and connections from said balanced primary windings to apair of input terminals.

WENDELL L. CARLSON. VERNON D. LANDON.

